640665357 has 8 divisors (see below), whose sum is σ = 854345184. Its totient is φ = 427047888.

The previous prime is 640665331. The next prime is 640665373. The reversal of 640665357 is 753566046.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a de Polignac number, because none of the positive numbers 2^k-640665357 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640665307) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19983 + ... + 40995.

It is an arithmetic number, because the mean of its divisors is an integer number (106793148).

Almost surely, 2^640665357 is an apocalyptic number.

It is an amenable number.

640665357 is a deficient number, since it is larger than the sum of its proper divisors (213679827).

640665357 is a wasteful number, since it uses less digits than its factorization.

640665357 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31179.

The product of its (nonzero) digits is 453600, while the sum is 42.

The square root of 640665357 is about 25311.3681376570. The cubic root of 640665357 is about 862.0724117908.

The spelling of 640665357 in words is "six hundred forty million, six hundred sixty-five thousand, three hundred fifty-seven".